Tag: comparison

Window replacement strictly for energy savings carries a big price tag that can be well out of range for many homeowners. Fortunately, there are several lower-cost options for reducing energy loss through windows that utility program managers might consider adding to their incentive offerings.

Window coverings can offer surprising energy benefits at a lower cost than window replacements, making them a good candidate for utility rebate programs. (Photo by DOE Office of Energy Efficiency and Renewable Energy)

Reflecting on film
Window films help block against solar heat gain and protect against glare and ultraviolet exposure. According to the International Window Film Association, professionally installed window film can block 30-60 percent of all energy being lost through window glass throughout the heating and cooling seasons. IWFA also claims that window film in commercial buildings can deliver seven times the energy saving benefits per dollar spent compared with installing replacement windows.

DOE’s Energy Saver blog explains that reflective films work best in climates with long cooling seasons, because they also block the sun’s heat in the winter. Other factors that impact the effectiveness of window films include:

Size of window glazing area

Window orientation

Building orientation

Whether the window has interior insulation

Incentives for professional installation of window films could be a winner for utilities serving low-income areas in warmer climates. Homeowners and businesses in such regions might welcome an affordable alternative to window replacement. Check with your state energy office to see if it offers any tax incentives you can piggy-back on your program.

Drawing on curtains, shades
Carefully chosen window attachments can also save homeowners energy for less than the cost of window replacements. The Attachments Energy Rating Council is a good place to begin exploring options. The two-year-old organization is working with DOE to provide credible and accurate information about the energy performance of residential and commercial window attachment products.

For an overview of AERC’s work, download “Window Attachments: A Call to Action,” the Council’s updated brief. AERC is holding its annual meeting in Annapolis, Maryland, May 22 to 24.

Efficient Window Coverings, a guide supported by DOE and Lawrence Berkeley National Laboratory, is another valuable resource for evaluating different window products for energy efficiency. Website visitors will find a calculator to help them choose the best covering for their circumstances and a comparison chart to see how coverings stack up against each other. These functions can help utilities identify a range of options to appeal to different customer segments.

Low wholesale power prices and an uncertain future for federal power regulations have made it trickier—and riskier—than ever for utilities and independent power producers to plan for and invest in generation.

Resource risk can be very difficult to mitigate for long-term investments in power plants, and it manifests differently for renewable and natural gas-fired generation. For renewables, the risk is “the quantity of wind and insolation will be less than expected.” For natural gas, the risk is “natural gas will cost more than expected.”

Statisticians label the mid-range case “P50,” but calculate a probability for all possibilities from P1 to P99. Probability of exceedance is commonly used by utility planners “to characterize the uncertainty around annual energy production for wind and solar projects,” the paper reports. It “can also be applied to natural gas price projections.”

The study’s “statistical concept” quantifies the risk at each P-level of expected renewables output levels and natural gas prices and factors them into a levelized cost of energy comparison. “In general, higher-than-expected gas prices appear to be riskier to ratepayers than lower-than-expected wind or solar output,” noted LBNL researcher and study co-author Mark Bolinger.

The disagreement underscores the importance of a method like LBNL’s that quantifies the risk and uncertainty. Renewable industry representatives have called the LBNL paper an important contribution that could be useful for utility integrated resource planning.

Read more about the study and industry reactions in Utility Dive and download the report and webinar presentations from the LBNL website.